As is well known, airbags are impact protection bags in automobiles. In the event of a crash, a control device triggers an inflation mechanism which fills the airbag with air within a split second and thus protects the passengers at least from serious injuries as may be caused by the effects of a crash impact.
In the past, airbag devices were installed in the dash face of the steering wheel. Since the control devices which trigger the inflation of the airbag are located outside of the steering wheel, the electrical connection between the airbag and the control devices must allow for relative turns between the former and the latter because the airbag turns with the dash face of the steering wheel while the control device is stationary.
To create this electrical connection, state of the art technology provides for the use of a spiral cable box containing a flat cable which is wound up spirally. The known spiral cable box is arranged between the steering column and the dash face of the steering wheel in such a way that one end of the flat cable contained in the spiral cable box is guided to the airbag in the dash face and the other to the control device, through the steering column.
The state of the art spiral cable box consists of a lower box part which is firmly connected with the steering wheel, and an upper box part which can be moved relative to the lower box part and is accommodated in the latter. The lower box part comprises two concentric cylinder walls, namely an inner cylinder wall and an outer cylinder wall, which are connected with each other through an annular disk wall. The cable spiral is placed into the cable receiving chamber of the lower box part which is open towards the top. The cable receiving chamber is closed off towards the top by an annular disk wall of the upper box part, adjacent to whose outer circumference there is an outer cylinder wall which is supported against the annular disk wall of the lower box part to set the distance between the annular disk wall of the lower box part and the annular disk wall of the upper box part.
One outlet piece each is provided on the annular disk wall of the upper and the lower box part to guide out angled end areas of the cable spiral. Through these outlet pieces one spiral cable end each must be guided after the cable spiral has been inserted into the spiral cable box. The ends of the spiral cable are provided with a plastic reinforcement material which serves to form the angled end areas of the spiral cable on the one hand and acts as a strain relief on the other hand. The cable reinforcements are either injected around or clipped onto the cable and are expensive to produce. Furthermore, they increase the cross section of the spiral cable in the angular end area which extends into the cable receiving chamber, an increase of size which is unfavorable for the installation of the spiral cable box. Furthermore, the larger cross section in the angular end area creates a relatively large free space between the cable spiral and the cable receiving chamber which is limited by the annular disk walls on top and on bottom. Therefore the cable spiral is axially movable, with the exception of the angular end areas, and this play may cause an undesirable clattering noise.
Furthermore, there is an additional handling process after winding up the cable spiral, when the cable spiral is inserted into the spiral cable box, either before or during its installation in the steering wheel. These additional handling processes are suspect as damage to the sensitive cable spiral by inexpert handling is a possibility. Also additional processes for installation of the sensitive cable spiral as well as installation at a number of windings different to those required for the neutral position of the steering wheel are required.
There is a need for an improved quiet cable box with cable spiral that can be assembled at the final place of installation and eliminates many unnecessary parts.